1. Field of the Present Invention
The present invention relates to a grindstone contact sensing method and its device, and a honing method and honing machine, and more particularly to a grindstone depth-cutting technique suited to honing technology of honing a honing grindstone while positively depth-cutting into the inner circumference of a work, mechanically at a specific depth of cut.
2. Description of the Related Art
In various machine tools for cutting and grinding a workpiece (hereinafter called a work) by using machining tools, it is required to specify the relative positions of the machining tool with the work, especially the contact position accurately, in order to judge the timing and control the operation for positioning the machining tool on the work, or depth-cutting.
For this purpose, a contact type sensor such as touch probe, or contact-free type sensor such as AE (acoustic emission) sensor is provided near the machining tool, and a contact sensing device for detecting the contact position of the machining tool with the actual work is used (see, for example, Japanese Patent Application Laid-Open No. 2005-262385).
However, in the machine tool provided with such contact position sensing device, an independent device is needed in addition to the machining tool, and the structure of the entire machine tool is larger in size and is complicated.
Such configuration is not applied in a narrow space of machining of the work, because the installation space for the sensor or the sensing space is not available.
Especially, in the honing process of finishing the hole inner circumference of the work to a mirror-smooth surface, since the honing grindstone is inserted into the hole of the work, the machining space is very narrow, and the contact sensing device used in a conventional general machine tool cannot be employed.
In such circumstances, in the conventional honing process, regardless of the contact position of honing grindstone with work, the final expansion amount of the honing grindstone (final depth of cut) is determined, and generally the honing process is executed to reach the target of this final expansion amount.
Recently, in machining of a pair of parts for male-female fitting, while one part is finished, the other part is finished to match with the first part, which is known as matching process or aiming process, and this matching process is most expected in the honing process for finishing the hole inner circumference of the work.
In this matching process or match honing process of the honing process, the depth of cut is determined from the contact position of the honing grindstone with the work inner circumference, and the contact position of the honing grindstone with the work is the processing reference position, and it is essential to detect the contact position. In the high-precision honing where the required finish precision is in the sub-micron unit, the sensing precision of contact position is also required at high precision of sub-micron unit.